[Mailman-Users] Retaining mails in inbox

[Jack Li]

Hi all:
I am currently managing a mailing list providing by mailman.
Recently I am thinking of archiving the mails into a forum.
The tools I am using to make that happen goes into the INBOX of an email
account to retrieve emails.
I have tested it with my personal email account and it works.
However, it seems that mailman doesn't keep the mails in inbox so I couldn't
retrieve any mail from it.
Is there a way to retain mails in in box?
Thanks in advance!

[PS: I am actually using "mailhandler", a module of drupal to get mails from
email account]